Drug discrimination procedures which measure the ability of animals to respond on the basis of their ethanol "intoxication" state will be utilized to study the interactions of other drugs with ethanol. Initial experiments with rats will assess the interaction of ethanol with lithium and chlordiazepoxide, as these agents are used in therapy and have been claimed to antagonize the effects of ethanol. Analogous experiments with squirrel monkeys will address the question of the generality across species of the drug discrimination findings. Other drugs that may have significant potential for interaction with ethanol will be evaluated in subsequent experiments. In conjunction with these studies which utilize ethanol as a discriminative stimulus, the secondary reinforcing properties of the drug will be determined. The repeated pairing of ethanol stimulus with a "tension relieving" event (the presentation of food to hungry animals) may predispose the animals to increase their consumption of ethanol in a subsequent free choice situation. Ensuing studies will include a comparison of the positive and negative secondary reinforcing properties of ethanol with those of other drugs.